Organic polysulfides and particularly dialkyl polysulfides such as tetra- and penta-sulfides have been found useful for many purposes such as additives for elastomers, antioxidants for lubricating oils, intermediates for the production of organic chemicals, insecticides, germicides and as an additive to diesel fuels to improve the cetane number and ignition qualities of these fuels. These compounds have also been found useful in the compounding of extreme pressure lubricants and in the acceleration of rubber treating processes.
Such polysulfide compounds can be prepared by reacting mercaptans with elemental sulfur in the presence of a basic catalyst. For example, Biensan et al (U.S. Pat. No. 3,308,166) discloses that polysulfides can be prepared from a mercaptan and sulfur catalyzed by an amine using an alcohol promoter.
A conventional process for producing a polysulfide compound such as di-t-dodecyl polysulfide is to react a mercaptan such as t-dodecylmercaptan with elemental sulfur in the presence of triethylamine as catalyst. However, the polysulfide thus prepared is associated with some unreacted mercaptans and residual H.sub.2 S contributing to unpleasant odor. Additionally, possibly because of the unreacted mercaptans and the amine catalyst, the product always becomes very unstable, i.e. the product turns cloudy, probably due to degradation of the polysulfide causing precipitation of sulfur. The instability along with the unpleasant odor greatly reduce the desirability and utility of the polysulfide product.
There is therefore a need to remove the odor associated with the product and to stabilize the product. Kamii et al (Japanese Application 58-140,063) discloses a process for deodorizing dialkyl polysulfides by contacting the polysulfide-bearing fluid with 1,2-epoxy compounds. The 1,2-epoxy compounds apparently react directly with the unreacted mercaptan and hydrogen sulfide, thereby producing a product with reduced odor. Excess 1,2-epoxy compounds are reportedly removed by conventional methods, such as vacuum distillation.
However, Kamii et al does not disclose any process for stabilizing a polysulfide compound. Additionally, the process disclosed in Kamii et al produces a product that still has such high a mercaptan level that it would contribute the instability of the polysulfide product. It would therefore be a significant contribution to the art to develop a process for the stabilization of such a polysulfide product so that the product is made more useful for industrial uses.